This invention relates to medical devices which are inserted into the body and located by X-ray imaging.
Various types of minimally invasive surgical techniques have been developed in recent years in which catheters or similar devices are used to convey a operative implement through a body passage, including such passages as the blood vessels, gastrointestinal tract, urethral and urethral tracts, bronchial and esophageal tracts, to a specific location where the implement is operatively employed or delivered. Catheters are used to perform balloon angioplasty, to deliver and lodge stent devices, to deliver drugs, to abrade or volatilize lesions, to remove temporary, misplaced or dislodged stents, and the like. For such activities, X-ray imaging is often used to follow the catheter or the operative implement as it traverses the body channel and/or to monitor the actual employment or deployment of the implement.
For materials which are transparent to X-ray, or are only weakly radiopaque, it has been conventional to provide radiopaque marker bands, coatings or laminates of more intensely radiopaque materials on the devices or implements in order to achieve the necessary contrast for a readily observable image.
A number of the implements, used or delivered by such techniques, or parts thereof may be made of metal or ceramic materials. Traditionally such implements are, or are made up of, small complex machined parts. Stents are an example of such an implement which is typically made by machining metal.
A technique which is known for manufacturing metal and ceramic parts utilizes injection molding and sintering of composite formulations. This technique, designated xe2x80x9cCIMxe2x80x9d for ceramic articles and xe2x80x9cMIMxe2x80x9d for metal articles utilizes formulations which are mixtures of a resinous binder material and a very fine powder of the respective ceramic or metal material, which is injection molded to produce a desired shaped article, the molded article typically being somewhat larger than the desired size. The binder is then typically removed by extraction, heating, or both, leaving a shaped structure of the powder material. This structure is sintered to form the final article, typically shrinking by a reproducible amount.
Similar products can be prepared from combining ceramic materials with metallurgic materials to form what is known as a xe2x80x9ccermet.xe2x80x9d
A porous stent formed by a powdered metal sintering process is disclosed in U.S. Pat. No. 5972027, incorporated herein by reference in its entirety. A perfusion tip for an ablation catheter is described in U.S. Pat. No. 6017338, incorporated herein by reference in its entirety.
The present invention is directed to articles which can be made using a CIM or MIM process, preferably articles which are, or are part, of surgical implement structures such as catheters, forcepts, stents, perfusion heads, electrodes, and the like used in minimally invasive surgical procedures and. The invention also relates to CIM or MIM processes for preparing such implements, or parts thereof, in which the ceramic or metal powder material used to form the article comprises a radiolucent material and a radiopaque material.
In a first aspect of the present invention there is provided a method for preparing an X-ray imageable article comprising:
(a) preparing a mixture composition comprising:
i) radiolucent particulate material selected from ceramic materials, metallurgic materials, and combinations thereof and having an average particulate size of no more than 40 microns,
ii) radiopaque particulate material selected from ceramic materials, metallurgic materials, and combinations thereof and having an average particulate size of no more than 40 microns, and
(iii) at least one polymeric binder material;
(b) injection molding the mixture composition into a preform;
(c) optionally removing the binder material from the preform; and
(d) sintering the preform.
Articles, especially surgical implements comprising an article composed of a sintered mixture of radiolucent and radiopaque powders as described herein, and medical devices comprising such implements are other aspects of the invention.
A further aspect of the invention is a surgical method in which a surgical implement as described herein is carried via a catheter to a remote site within the body and used in performing a surgical procedure, wherein the article of the invention is observed fluoroscopically during at least a portion of the time it is in the body.
Still further aspects of the invention are described in the detailed description below and in the claims.